senators assessed with varying degrees of confidence that assad's government used a chemical agent sarin on a small scale. they have emphatically denied this. but if it turns out there is unequivocal evidence of sarin use, they have used weapons of mass destruction, chemical weapons and so on, obama would have to do something, wouldn't he? >> i don't know he would have to do something. the argument that he may have made an error in putting that red line in place may be a valid argument. but this is such serious business. i understand the question. i understand that the dilemma that not only the president of the united states is in but our country is in that you say, look, if they use chemical weapons, that's a red line and there'll have to be a price for that. but, again, what do we do? a no-fly zone sounds easy, but the first time an american aircraft is down, an effort to rescue the pilot, i just come back to you have to be careful what you get into because getting out of it is extremely difficult. this syrian situation, when i say we need a national debate, we really haven't had a nat